( 101 ) 



eines Gleichgewichtziistandes resultiren" ; «-iiiethylgliicosidc is then 

 always present in the lai-gest quantity. 



2. My research bas now led to the following resulls. 



If we start on the one hand from pure «- and on the oilier hand 

 from pure /?-methylglucoside ^) the methylalcoholic solution of HCl 

 arrives in both cases at the same condition of equilibrium in which 

 the «-and i5-compounds are both present. After removing the HCl. 

 with PbCOj and evaporating the solvent a crystalline mass was left 

 which was extracted with acetic ether. This on evaporation yielded 

 an extremely small quantity of a non-crystallisable product [at most 

 10 milligr. from 2.5 gram of «-glucoside] which may possibly be 

 Fisher's dimeth3'lacetal. Its concentration is, therefore at any rate 

 exceedingly small in comparison with those of the two glucosides. 



3. From the rotation of the solution, after equilibrium is attained, 

 it may be found by calculation that 77 7o of the glucoside is present 

 in the «- and 23 7o ^^ the i?-form. 



From the change in rotation with the time the velocity, with 

 which the transformation takes place, may be calculated. It appears 

 that the formula for a non-complete unimolecular reaction is appli- 

 cable here; 



-- = k(a — .v) — k' (a' 4- .v) ') 

 dt \ \ J I 



\a and a' are the concentrations of the two glucosides at the moment 

 the measurement begins, cc is the quantity converted after the time t\. 

 By integration this formula gives 



1 *^ 



k ^k! = - Ig ?^— ; 



t A' .V 



00 



.v^ is the total quantity converted from t = to t = co . 



k-{-k' remained satisfactorily constant during the reaction both 

 when the «- and when the |3-glucoside was used, and led in both 

 cases to the same figure. With a 1.34 normal solution of HCl in 

 methylalcohol k-\-k' at 25° was found to be 0.0051; (the time 

 expressed in hours); the transformation at (hat HCl-concentration 

 therefore proceeds tolerably slowly ; tiic equilibrium is practically 

 attained after about 20 days. 



4. The result of the velocity determinations is most simply expressed 

 by supposing that the reciprocal transformation of the two isomers 

 represents an intramolecular migration, in this way: « ^ <:?. The in- 



1) I have to thank Mr. Alberda van Ekenstein for kindly supplying me with a 

 certain quantity of these two substances. 



2j This formula has been first applied by Kistiakowsky to esterification. 



